1. Field of the Invention
The present invention relates to an image reading apparatus. More particularly, the present invention is suitable for an image reading apparatus such as an image scanner, a copying machine, a facsimile machine, or the like.
2. Description of the Related Art
In an image reading apparatus configured to illuminate a surface of original to read an image thereon by a line sequential system, an illuminating device using a light emitting diode (LED) as a light source is hitherto used. Japanese Patent Application Laid-Open No. H10-190962 discloses an illuminating device of an edge lit type in which an LED is provided at an edge in a longitudinal direction of a light guide and a light flux is reflected in the light guide to be guided to an original. Further, in recent years, a structure is known in which, in order to realize higher quality of an image read by an image reading apparatus, a reduction optical system having a deep depth of field is adopted to enhance light collecting efficiency in a section perpendicular to the longitudinal direction of the light guide.
However, when a reduction optical system is applied to the structure disclosed in Japanese Patent Application Laid-Open No. H10-190962, a light flux that is regularly reflected by the surface of original is collected on a sensor through the reduction optical system, and a bright spot appears in a read image.